Microcornea, Posterior Megalolenticonus, Persistent Fetal Vasculature, and Coloboma Syndrome Associated With a New Mutation in ZNF408

Identification and Characterization of ATOH7-Regulated Target Genes and Pathways in Human Neuroretinal Development

The proneural transcription factor atonal basic helix-loop-helix transcription factor 7 (ATOH7) is expressed in early progenitors in the developing neuroretina. In vertebrates, this is crucial for the development of retinal ganglion cells (RGCs), as mutant animals show an almost complete absence of RGCs, underdeveloped optic nerves, and aberrations in retinal vessel development. Human mutations are rare and result in autosomal recessive optic nerve hypoplasia (ONH) or severe vascular changes, diagnosed as autosomal recessive persistent hyperplasia of the primary vitreous (PHPVAR). To better understand the role of ATOH7 in neuroretinal development, we created ATOH7 knockout and eGFP-expressing ATOH7 reporter human induced pluripotent stem cells (hiPSCs), which were differentiated into early-stage retinal organoids. Target loci regulated by ATOH7 were identified by Cleavage Under Targets and Release Using Nuclease with sequencing (CUT&RUN-seq) and differential expression by RNA sequencing (RNA-seq) of wildtype and mutant organoid-derived reporter cells. Additionally, single-cell RNA sequencing (scRNA-seq) was performed on whole organoids to identify cell type-specific genes. Mutant organoids displayed substantial deficiency in axon sprouting, reduction in RGCs, and an increase in other cell types. We identified 469 differentially expressed target genes, with an overrepresentation of genes belonging to axon development/guidance and Notch signaling. Taken together, we consolidate the function of human ATOH7 in guiding progenitor competence by inducing RGC-specific genes while inhibiting other cell fates. Furthermore, we highlight candidate genes responsible for ATOH7-associated optic nerve and retinovascular anomalies, which sheds light to potential future therapy targets for related disorders.

Unrecognized ROPER in a child with a novel pathogenic variant in ZNF408 gene

BACKGROUND

Familial exudative vitreoretinopathy (FEVR) is a rare hereditary disorder characterized by abnormal or incomplete retinal angiogenesis commonly inherited in an autosomal dominant fashion. Up to 50% of FEVR cases are linked to known genetic mutations affecting retinal vasculature development.

PURPOSE

To report a case, a novel pathogenic variant of the ZNF408 gene associated with a case of FEVR in a premature male.

MATERIALS AND METHODS

Case report.

RESULTS

A 10-month-old male who was born prematurely at 34 weeks' gestation in the Dominican Republic was referred for persistent avascular retina. The baby was treated with bilateral intravitreal ranibizumab injections for retinopathy of prematurity (ROP) with the presence of plus disease. Fundus examination several months after treatment revealed the absence of tortuosity of the vessels with avascular periphery; fluorescein angiography (FA) confirmed peripheral avascularity and demonstrated irregular sprouts of vascularization in the absence of neovascularization. We performed genetic testing under the suspicion of FEVR and results identified a heterozygous mutation in the ZNF408 gene on chromosome 11, c.1307 C > T.

CONCLUSION

FEVR is an important differential diagnosis in premature infants with retinopathy, as clinical presentation can overlap with common findings in ROP. Maintaining high suspicion for the disease is especially critical in cases with findings unusual for ROP. FEVR in the presence of prematurity has been well described, falling under the proposed term ROPER. Genetic testing is key to confirm diagnosis.

Corneal Biometric Parameters and Refractive Properties in Microcornea With Normal Axial Length

PURPOSE

The purpose of this study was to evaluate the features of and relationships among corneal diameter, central corneal thickness (CCT), endothelial cell density (ECD), and corneal refractive properties in cases of microcornea (MC) with normal axial length.

METHODS

We included 22 patients (35 eyes) with MC and cataracts and 41 patients (48 eyes) with isolated cataracts as age-matched controls. They were divided into patients with MC younger than 18 years (MC-child), patients with MC 18 years or older (MC-adult), children with congenital cataracts (CCs), and adults with senile cataracts (SCs). Corneal diameter, axial and anterior chamber length, and keratometry were measured; central corneal endothelial cell imaging was performed.

RESULTS

The mean horizontal corneal diameter was 7.71 ± 1.51 and 8.78 ± 0.52 mm in MC-child and MC-adult groups, respectively, and 11.89 ± 0.59 and 11.52 ± 2.42 mm in child and adult controls, respectively. The mean CCT was 641.26 ± 63.37 (MC-child) and 617.38 ± 45.40 mm (MC-adult), and 554.92 ± 34.64 (CC) and 551.58 ± 28.47 mm (SC). The mean ECD was 2898.47 ± 443.90 (MC-child) and 2825.81 ± 484.65 cells/mm 2 (MC-adult), and 3155.13 ± 372.67 (CC) and 2749.33 ± 399.63 cells/mm 2 (SC). The average keratometry was 44.22 ± 3.14 D (MC-child) and 43.86 ± 2.59 D (MC-adult), and 44.19 ± 1.44 D (CC) and 43.94 ± 1.34 D (SC).

CONCLUSIONS

Patients with MC and normal axial length possess specific parameters, including significantly smaller corneal diameter and thicker CCT than the patients in the control groups. There were no significant differences in ECD and average keratometry. These parameters should be taken into account in the follow-up and treatment.

Identification of Key Genes and Pathways in Persistent Hyperplastic Primary Vitreous of the Eye Using Bioinformatic Analysis

Background: The failure of the embryonic hyaloid vascular system to regress naturally causes persistent hyperplastic primary vitreous (PHPV), a congenital eye disease. PHPVs molecular pathway, candidate genes, and drug targets are unknown. The current paper describes a comprehensive analysis using bioinformatics to identify the key genes and molecular pathways associated with PHPV, and to evaluate potential therapeutic agents for disease management. Methods: The genes associated with PHPV were identified using the pubmed2ensembl text mining platform. GeneCodis was employed to evaluate the Gene Ontology (GO) biological process terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Search Tool for the Retrieval of Interacting Genes (STRING) constructed a protein-protein interaction (PPI) network from the text mining genes (TMGs) in Cytoscape. The significant modules were clustered using Molecular Complex Detection (MCODE), and the GO and KEGG analysis for the hub genes were analyzed with the Database of Annotation, Visualization and Integrated Discovery (DAVID) tool. ClueGO, CluePedia, and ShinyGo were used to illustrate the functions and pathways of the clustered hub genes in a significant module. The Drug-Gene Interaction database (DGIdb) was used to evaluate drug-gene interactions of the hub genes to identify potential PHPV drug candidates. Results: A total of 50 genes associated with PHPV were identified. Overall, 35 enriched GO terms and 15 KEGG pathways were discovered by the gene functional enrichment analysis. Two gene modules were obtained from the PPI network constructed with 31 nodes with 42 edges using MCODE. We selected 14 hub genes as core candidate genes: TP53, VEGFA, SMAD2, CDKN2A, FOXC, FZD4, LRP5, KDR, FZD5, PAX6, MYCN, NDP, PITX2, and PAX2, primarily associated with camera-type eye morphogenesis, pancreatic cancer, the apoptotic process involved in morphogenesis, and the VEGF receptor signaling pathway. We discovered that 26 Food and Drug Administration (FDA)-approved drugs could target 7 of the 14 hub genes. Conclusions: In conclusion, the results revealed a total of 14 potential genes, 4 major pathways, 7 drug gene targets, and 26 candidate drugs that could provide the basis of novel targeted therapies for targeted treatment and management of PHPV.

Down syndrome with bilateral posterior lenticonus

We present a case of bilateral posterior lenticonus in a young boy with Down syndrome. Association of posterior lenticonus in Down syndrome is rarely reported in the literature. We have discussed the clinical features and management of this patient at our hospital.

Diagnostic and Management Strategies in Patients with Persistent Fetal Vasculature: Current Insights

Persistent fetal vasculature (PFV), previously known as persistent hyperplastic primary vitreous, is a developmental malformation of the eyes that is caused by a failure of the hyaloid vasculature to regress in utero. PFV has been reported for decades; however, our understanding of the pathophysiology/pathogenesis of PFV, and the diagnostic and treatment modalities for PFV have evolved over time, and these advancements have improved diagnosis, treatment, and outcomes. However and in spite of these advancements, the heterogeneity of this disease continues to make PFV a diagnostic challenge. Here, we review what is currently known about various important aspects of PFV to update and enhance the knowledge of ophthalmologists who encounter and manage PFV in clinical practice.

Total retinal detachment and contractile movement of the disc in eyes with morning glory syndrome

Purpose

This study aimed to report clinical characteristics, intraoperative findings, and surgical outcomes of 2 eyes of 2 patients with retinal detachment (RD) associated with morning glory syndrome (MGS) and contractile movement of the disc.

Observations

Case 1 was a 3-year-old Japanese boy who presented with congenital microphthalmos in the left eye. The presence of total RD with MGS and contractile movement of the disc was confirmed by ophthalmoscopic examination. During vitrectomy, migration of perfluorocarbon liquid into the subretinal space was observed, suggesting a communication between the vitreous cavity and the subretinal space. Here, the retina was reattached briefly after the surgery; however, it detached again 2 months after surgery. Case 2 was a 3-month-old Japanese girl who was referred to our hospital for evaluation of RD and MGS in her left eye. Partial RD, MGS, and contractile movement of the disc were confirmed by ophthalmoscopic examination. The RD remained unchanged up to 18 months from the first visit, but atresia of the pupil was found 21 months after the first visit. Severe proliferative vitreoretinopathy and contractile movement of the disc were found after lensectomy. It was impossible to completely remove the membrane despite meticulous effort of peeling it off. At the 15-month follow-up, the retinal configuration improved but remained detached.

Conclusion and importance

Total RD with contractile movement of the disc associated with MGS is a rare condition that seems difficult to treat.

Ocular coloboma: Genetic variants reveal a dynamic model of eye development

Ocular coloboma is a congenital disorder of the eye where a gap exists in the inferior retina, lens, iris, or optic nerve tissue. With a prevalence of 2-19 per 100,000 live births, coloboma, and microphthalmia, an associated ocular disorder, represent up to 10% of childhood blindness. It manifests due to the failure of choroid fissure closure during eye development, and it is a part of a spectrum of ocular disorders that include microphthalmia and anophthalmia. Use of genetic approaches from classical pedigree analyses to next generation sequencing has identified more than 40 loci that are associated with the causality of ocular coloboma. As we have expanded studies to include singleton cases, hereditability has been very challenging to prove. As such, researchers over the past 20 years, have unraveled the complex interrelationship amongst these 40 genes using vertebrate model organisms. Such research has greatly increased our understanding of eye development. These genes function to regulate initial specification of the eye field, migration of retinal precursors, patterning of the retina, neural crest cell biology, and activity of head mesoderm. This review will discuss the discovery of loci using patient data, their investigations in animal models, and the recent advances stemming from animal models that shed new light in patient diagnosis.

Molecular genetics of congenital cataracts

Congenital cataracts, the most common cause of visual impairment and blindness in children worldwide, have diverse etiologies. According to statistics analysis, about one quarter of congenital cataracts caused by genetic defects. Various mutations of more than one hundred genes have been identified in hereditary cataracts so far. In this review, we briefly summarize recent developments about the genetics, molecular mechanisms, and treatments of congenital cataracts. The studies of these pathogenic mutations and molecular genetics is making it possible for us to comprehend the underlying mechanisms of cataractogenesis and providing new insights into the preventive, diagnostic and therapeutic approaches of cataracts.